This invention relates to isolation devices and more particularly to isolation devices which use an optical channel to isolate a remote circuit from a source circuit.
In certain environments it is necessary to establish substantial electrical isolation between electrical control and power circuits. An example of such an environment is an electric hospital bed. Bed motion control circuits are often found in side rails, footboards, headboards, and in pendants connected via an umbilical cord to the motor power circuits. Metal and other conductive surfaces may be incidentally contacted by patients, caregivers, and even critical care equipment. When contact is made, a potential hazard exits if the conductive surface provides a path for current flow to earth ground. For this reason, regulatory bodies impose strict requirements on patient connected equipment and identify equipment in regard to its insulation abilities.
Having non-isolated electrical control circuitry in exposed areas such as side rails and footboards, presents a challenge to design engineers. It is known to provide power to a remote isolated circuit with an isolated power supply and send optically isolated control signals from the remote isolated circuit to the local source circuit which controls actuators powered by a non-isolated power supply. Signals generated by the remote isolated circuit are optically transmitted to the local source circuit and power to the remote isolated circuit is provided through bulk cables from the isolated power supply. However, isolated power supplies can be very costly.
The optical isolation device of the present invention transmits power from a power supply on a local source circuit optically along an optical channel to a remote isolated circuit. Signals generated by the remote isolated circuit are optically transmitted to a local source circuit which controls various actuators. Thus the remote isolated circuit is completely electrically isolated from the local source circuit.
An optical isolation device for transmitting power to and signals from an isolated electrical device in accordance with the present invention includes a light source for generating light, an optical channel having a first end on which the light impinges and a second end optically coupled to the first end, and an opto-electrical detector adjacent the second end producing electrical power to drive the isolated electrical device when impinged upon by the light. An optical signal generator generates optical signals in response to input provided by the isolated electrical device, the optical signals impinge upon the second end of the optical channel and are transmitted to an opto-electrical sensor adjacent the first end of the optical channel that generates electrical signals in response to the optical signals. The light and optical signals are both propagated through the optical channel.
Also in accordance with the invention is an opto-electric device including a first circuit having a first light source, a second circuit having a second light source, and a photovoltaic cell configured to provide energy to at least a portion of the second circuit. An optical channel couples the first and second circuits, and light from the first light source is transmitted to the photovoltaic cell over the optical channel, and light from the second light source is transmitted to the first circuit over the optical channel.
A method of the present invention for electrically isolating a remote circuit from a source circuit includes the steps of generating a first light signal in the source circuit, optically coupling the first light signal to the remote circuit so that the remote circuit receives the first light signal from the source circuit, generating power in the remote circuit from the first light signal received by the remote circuit, and powering the remote circuit by the generated power.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of illustrated embodiments exemplifying the best mode of carrying out the invention as presently perceived.